Chaosium, (kay-OSS-ee-yum) is known for publishing high quality books & games, and for having a well-developed sense of fun.

In 1975 we were founded as The Chaosium. In 1980 we incorporated as Chaosium Inc. Chaosium thrives in the mild climate, gorgeous surroundings, and gentle earthquakes of the San Francisco Bay Area.

Our main office is in Hayward, located about half-way between San Francisco and San Jose. A short walk away is a very good micro-brewery (and one of the oldest!) and Charlie Krank’s home. Charlie is our president and resident BBQ expert.

Most of Chaosium's product lines are based upon literary sources. H.P. Lovecraft's 1920's horror fiction provides the basis of our classic Call of Cthulhu roleplaying game line which has won so many awards that we have lost count, though we do know that there are more than 70 of them. Mr. Lovecraft also provides the inspiration for our many Chaosium Fiction collections. We are now expanding our fiction offering to include other, related, genres.

Horror Roleplaying in the Worlds of H. P. Lovecraft
The Great Old Ones ruled the earth aeons before the rise of humankind. Originally they came from the gulfs of space and were cast down by even greater beings. Remains of their cyclopean cities and forbidden knowledge can still be found on remote islands in the Pacific, buried amid the shifting sands of vast deserts, and in the frigid recesses... [click here for more]

Horror Roleplaying in the Worlds of H.P. LovecraftThe Great Old Ones ruled the earth aeons before the rise of humankind. Originally they came from the gulfs of space and were cast down by even greater beings. Remains of their cyclopean cities and forbidden knowledge can still be found on remote islands in the Pacific, buried amid the shifting sands of vast deserts, and in the frigid recesses... [click here for more]

The Chaosium System
Welcome to Chaosium’s Basic Roleplaying system, a book that collects in one place rules and options for one of the original and most influential role playing game systems in the world.
This book comprises a roleplaying game system, a framework of rules aimed at allowing players to enact a sort of improvisational radio theater—only without microphones—and... [click here for more]

Horror Roleplaying in the Worlds of H.P. Lovecraft
The Great Old Ones ruled the earth aeons before the rise of humankind. Originally they came from the gulfs of space and were cast down by even greater beings. Remains of their cyclopean cities and forbidden knowledge can still be found on remote islands in the Pacific, buried amid the shifting sands of vast deserts, and in the frigid recesses... [click here for more]

In this BRP Quick-Start booklet, Chaosium has collected the essential Basic Roleplaying rules for a quick introduction to one of the most influential roleplaying systems in the world.
Basic Roleplaying was designed to be intuitive and easy to play. Most Basic Roleplaying mechanics are simple and logical.
Virtually all rolls determining success or failure of a task are... [click here for more]

Call of Cthulhu Roleplaying in the Year 1000 A.D.
The Dark Ages world is filled with life, death, and the pain of old age. Vengeful hordes wash across the world. Petty warlords fight among themselves like ravenous dogs. Disease runs rampant. Illiterate city-folk and simple farmers dread that which lurks in the dark. And in the greatest abbeys, a few know of forbidden books that speak of blasphemy... [click here for more]

Science is an Illusion, History is a Lie.
In ages past you lived many times. Your slaves built the Great Pyramid to honor your death; you died for the sins of Jerusalem; you lost your head suggesting they eat cake.
You are Nephilim – demi-god, prophet, saint, & magician from the mythic past.
Again you incarnate, to continue your ancient struggle for enlightenment,... [click here for more]

Defend Justice and Smash Evil With Your Superworld Heroes
Welcome to the universe of comic book super heroes, where mighty guardians of truth and justice struggle against he machinations of ruthless supervillains. Recreate favorite comic book heroes and create new ones with the powers and abilities of your choice! Using a large selection of superpowers you will prepare your beginning characters for... [click here for more]

An Essential Guide for Players
When faced with the horrors of the Cthulhu Mythos, investigators need all the help that they can get. This essential player's aid for Call of Cthulhu provides it.
The 1920s Investigator's Companionis split into four sections. "The Roaring Twenties" details life in the 1920s, from a general historical overview to listing of favorite songs, books,... [click here for more]

The ideas presented in this book attempt to be both mundane and fantastic at the same time— plausability is the key.
It is in the details that the horror lies, because it is in the credibility of the details that the fantastic can rise and stand.
This, then, is a book of details, most mundane, some fantastic. They have but one purpose—that of bringing Lovecraft's horror home to us... [click here for more]

Terrifying Tools and Reality-Wrenching Rules for Players and Keeper Alike
Call of Cthulhu is, of course, an excellent role-playing system and one that easily lends itself to expansion in many areas. In keeping with that spirit, this book explores a number of optional expansions to the original Call of Cthulhu rules-primarily in the areas of new, specialized skills; new spells, books,... [click here for more]

A Modern Military Adventure for Basic Roleplaying
A Chinese nuclear submarine bearing a dozen missiles,each with a nuclear warhead, reported a major mechanical malfunction and would return to port. The ship is late. World governments receive a broadcast from the captain of the lost submarine, demanding that Japan, Taiwan, and South Korea surrender to the Peoples Republic of China by midnight --... [click here for more]

A Resection of Time is a short campaign for Call of Cthulhu set in the modern day. It begins in early April, in San Francisco, and ends a little later in the steamy jungles of Belize, in Central America. Before plunging into the dark heart of the ancient Mayan world, the investigators also travel to Los Angeles and shadowy Arkham.
The details of Mayan architecture, culture, epigraphy,... [click here for more]

The Mythic West
ACES HIGH is a mythical, western role-playing game where Davey Crockett exists along side The Man With No Name. The relationship, however, may be an uneasy one.
Violence is an everyday occurrence on the frontier of Civilization. Dust swirls around a crimson sun, reminding every one of their possible success, telling them of their mortality. Settlers make a grab for... [click here for more]

Welcome to New Mexico 1875! Land of Enchantment
Aces High: New Mexico, Dark Days in the Land of Enchantment, is a companion book for Chaosium‘s Aces High BRP supplement. Aces High: New Mexico is split into two sections; the first section is concerned with historical, geographical and societal issues that will allow the Master to explore... [click here for more]

Demons, Necromancy & High-Level Magic
The worlds of fantasy are vast and diverse. Whether steeped in philosophy and existentialism, or action and carnage, the one commonality to all tales of fantasy is the influence of the supernatural on the natural world. Mages, wizards and sorcerers force the world to bend to their will. They grab the the fundamental essence of the universe and force... [click here for more]

Super Agents in Victorian England Serving Queen and Country
AGENTS OF THE CROWN combines Victorian heroic action in the tradition of pulp stories, comic books, and the Penny Dreadfuls of the 19th century with the solid play and tremendous versatility of the Basic Roleplaying system.
Agents of the Crown allows players to take the roles of super-agents in Victorian... [click here for more]

This book is an encyclopedia of the strange, the bizaare, and the deadly. It contains complete statistics for 265 monstrous and dangerous creatures, created by dungeon masters across the United States and Canada. Each monster is rated for hit dice, armor class, movement, whether and how well it swims and flies, its intelligence range, dexterity, alignment, normal habitat, the probability of it being... [click here for more]

In its third printing, volume II of the ALL THE WORLDS’ MONSTERS series contains 243 creatures from literature, fantasy, and nightmare. Included is a conversion article by Ken St. Andre for TUNNELS & TROLLS, and Steve Perrin’s historic “Conventions.” Created by 54 DMs from across North America, each monster is rated for hit dice, armor class, movement, whether or how well... [click here for more]

Now! The long-wanted 3rd volume of the All the Worlds’ Monsters series is here-112 pages packed with monsters and play-aids. Included are 238 new monsters, an all-series index, a RuneQuest stats conversion essay by Steve Perrin, and grouping lists by monster type, level, and appearance. The stats were created by dungeon masters from across the United States and Canada. Each monster is rated for... [click here for more]

Revisiting the Legend-Haunted City
ARKHAM NOW updates to modern times the famous and fabled city of Arkham for the Call of Cthulhu roleplaying game.
Most residents believe there is only one horror lurking in this legendary haunted town — the urban sprawl slowly eroding Arkham's old New England beauty. Rushing by neon signs and mega-marts to obtain even more material possessions,... [click here for more]

The batle against the horrors of the myihos often leaves an investigator dead or insane. In either case, a paper trail has formed, one that can lead new, ignorant investigators into realms of unspeakable evil.
This supplement contains a large number of useful forms for use in a Call of Cthulhu® game. Death certificates, insanity certificates, patient records, and even fingerprint forms... [click here for more]

EXPLORING THE DARKER SIDE OF HUMAN NATURE
The world is not a happy place. This Basic Roleplaying setting casts the adventurers as mavericks in a fantasy world that is losing a war it does not even know that it is fighting. Hidden demons and their mortal minions-many of whom do not even know who their masters truly are-manipulate events from the shadows, experimenting with social control mechanisms... [click here for more]

Pulp Adventures for Basic Roleplaying
Welcome to the heart-pounding, two-fisted, action-filled world of the Pulps! Throughout this book you will find Basic Roleplayingrules for new character types, skills, combat, magic, mad science, and a plethora of villains, henchmen and monsters.
Accompanying the text are several sidebars containing special, optional rules to... [click here for more]

MYTHOS HORROR IN THE 1950sNEVER BEFORE had the world faced a threat as potentially devastating as the A-bomb -- and the even more lethal H-bomb that followed. Educational films showed how to "survive" a nuclear blast by crawling under a desk, as if a few inches of wood made any difference. In movie theaters, classic monsters of the '30s and '40s were replaced by... [click here for more]

Teenage Superheroes Tackle the Syndicate!
Dr. Drugs had a nice retail outlet at Warren G. Harding High School, and his pills, poppers, and nastier substances went at bargain prices - to the Doctor, who dreamed of turning-on all of humanity to the way of drugs, profit was inconsequential (though his syndicate backers hardly thought so).
But, after a student-customer overdoses and dies, the Doctor... [click here for more]

Running the Chaosium Roleplaying System
This book provides wisdom and advice on running Basic Roleplaying games. There are five main sections: the first discusses the duties of the gamemaster in devising and presenting roleplaying adventures. The second covers scenario-construction aids for the gamemaster including encounter tables, languages, treasures, and danger-classes. The third treats... [click here for more]

FOUR NATIONS, TWO SIDES, ONE CITY. WHO DO YOU BELIEVE?
A setting for different BASIC ROLEPLAYING genres. Includes information on life in the city during the cold war, key locations, and special organizations. Battle spies, assassins, cultists and the Dark Herald Kototh. A great back-drop for espionage adventures in the 1960s style, and silver age superhero action!
NOTE: this work was... [click here for more]

An Epic Antarctic Campaign & Sourcebook
Little by little they rose grimly into the western sky; allowing us to witness the various bare, bleak, and blackened summits . . . in the reddish Antarctic lights against the provocative background of iridescent ice-dust clouds. In the whole spectacle there was a persistent, pervasive hint of stupendous secrecy and potential revelation. . . . I could... [click here for more]

Evil Cults for Call of Cthulhu
This book contains a collection of modern-day organisations for use in your Call of Cthulhu games. The Church of a Thousand Tomorrows can nuke you from orbit, while the Sufferers' Guild could be brought down with a few well-placed phone calls. More importantly, all the personalities described have reasons for the things they do. Some of the characters want... [click here for more]

The year is 1855. Perfection is a small gold-mining town located on the east side of the Rocky Mountains, in the Kansas Territories. The state of Colorado has not yet been established. The impetuous daughter of a rail-baron left home to experience the Western Frontier. For three months there has been no word from her. Pinkerton Agents are now on the case, hired to find Victoria Featherstone amid the... [click here for more]

13 Titillating Tales
"...and I would have got away with it too if it hadn't been for you meddling investigators and your stupid dog!"—Frustrated Cultist upon arrest by local authorites.
Do you have gaming buddies coming over tonight and don't know what to wear, or more importantly what game you'll run? Blood Brothers to the rescue! We'll... [click here for more]

9 Glimpses of Horror"Ooh, those A-li-ens, A-li-ens On a weekend from Mars They liked our girls and our cars- Ooh, those A-li-ens, A-li-ens" —From the Blood Brothers 2 soundtrack.
They're B-movies, they're bad, and they're back for more laughs. Nine scenarios which have more to do with bad horror films than with H.P. Lovecraft. Microwave the popcorn,... [click here for more]

Black Sails & Dark RitualsTHE GOLDEN AGE OF PIRACY is a time when men turn their hands against each other and the seas and coasts are splattered with blood.
The wars that ravaged Europe are over, but peace brings new problems. Thousands have been displaced or orphaned, their homes and lands ruined or claimed by others. Many thousands more see their livelihoods as soldiers and... [click here for more]

Autumn — the time of the Festival of the Dead, when the veil between the worlds is thinnest and prayers to ancestors easiest made. Pumpkin cakes are left in the Ancestors' Niche in every house, and children tie black and orange ribbons to the doors and put candles in the windows of their houses so their dead ancestors can easily find their way home.
It is a quiet time, after the harvest... [click here for more]

BRP ADVENTURES presents thirteen adventures for the Basic Roleplaying system. These are drawn from the submissions for the first Basic Roleplaying Adventure Contest. Organized by genre, these stories illustrate the versatility of BRP and its adaptability to different kinds of storytelling. The following are the general genres and adventures included:
FANTASY
* Sharazar,... [click here for more]

The village wise-woman creating herbal mixtures to cure her neighbours of the latest plague to curse their homes, the crone who disguises herself as a beautiful young woman to entice men to their doom, the travelling warlock who trades in potions and talismans which may or may not be truly magical. These are all examples of witches; men and women for whom witchcraft is an art and a profession.
Within... [click here for more]

Three Cthulhu Dark Ages Adventures
This monograph constitutes Chaosium's first GenCon tournament for Cthulhu Dark Ages. The staffers chose the Latin name, which translates to "the approaching darkness". It also makes for a nifty acronym that fits in well with the Lovecraft Mythos.
The first scenario, Island of the Damned takes tough-as-nails Viking characters completely out... [click here for more]

Constable Clark of Coldwater Falls, was desperate for attention. He'd been in touch with every sanatorium and hospital from New York to Boston and there's not an empty bed to be found since the stock market crash of last year. They're full to brimming with suicidal businessmen and investors. He is holding a man in his jail exhibiting some rather extraordinary behaviors. The delusion is complete... [click here for more]

Modern-Day Non-Player Characters
This is a collection of 120 Modern-Era NPCs for overworked keepers to use in their games and campaigns. These NPCs are ones typically found in society and can provide useful information, assistance, or adventuring opportunities for Investigators. All are complete with Statistics, skills, a physical description, and a brief, but highly individualized... [click here for more]

Call of Cthulhu in the Great Depression
Experts predict that the want and suffering of the Great Depression will create "a generation of cannibals." Panicked people flee their homes to escape a devastating invasion and poison gas attack. Life comes to a standstill as people watch a strange dust descend from the sky.
The spread of the Great Depression and the first rumblings of... [click here for more]

Five Tales for a Not-So-Silent Night
Some time ago we asked you to submit adventures concerning the holiday season. This monograph contains five tales certain to scare the stockings off the mantle.
Silent Night
Set in Arkham in December of 2001, this tale involves four investigators gathered to celebrate the season, the mythos far away for the moment.
The Gaudy
The investigators are invited... [click here for more]

This book contains several new resources for the player and gamemaster of Nephilim. At the front of the book are sixteen new Past Life eras for character generation. These eras also help fill in some of the timeline of Nephilim history.
Following the new Past Life eras is a section of new Metamorphosis rules which change the way in which the Transformations work, and introduce the idea of passionate... [click here for more]

"The times were lawless and the men who had flouted the King's Revenue forces for years were not the ones to balk at sterner things when duty impelled." —H.P. Lovecraft "The Case of Charles Dexter Ward" Colonial Terrors is a Call of Cthulhu campaign taking place in New England just prior to the American Revolution. The investigators... [click here for more]

Horror Roleplaying in 1890s England
IN THE 1890s, Cthulhu and his minions share the globe with the mighty British Empire. But they owe allegiance to an empire of their own — a dark and cruel design on ownership of the world and on the dreams of humanity. Even among the green fields of rural England, only thoughtful and energetic intervention keeps the shadows at bay.
CTHULHU... [click here for more]

Ghastly Adventures & Erudite Lore
This book is composed of submissions to Different Worlds magazine and other Cthulhoid Chaosium projects. The Different Worlds readers’ enthusiasm for the Cthulhu Mythos resulted in many excellent submissions, some of which appear, with permission, within these pages.
The contents of this supplement are quite varied. The first two... [click here for more]

The Aeon of the Elder Party Has Arrived!
A 9th Level Beer and Pretzels Role-Playing Game.* Have you lost all hope in the future? Tired of Big Government? Sick of greedy, corrupt officials? You are not alone! Become one with the Elder Party! The greatest evil in the universe just sunk to new depths, and has announced his intention to enter politics. Don't settle for the lesser evil! Heed the... [click here for more]

Horror Roleplaying in Ancient Rome
ROMAN CHILDREN TREMBLE in their beds as their mothers tell them stories of Medusa, the Hundred-Handed Ones, and the War of the Titans. They pray that the Fates have woven a long skein for them, free from encounters with the Minotaur and Cerberus. Little do they know that things more horrible than the creatures of myth and legend inhabit the world. A dark god... [click here for more]